Up until yesterday it was only possible to link one AdWords account to your Analytics account.
Starting yesterday, you can now link multiple AdWords accounts to your Google Analytics account.
The new data sources section in your Google Analytics account settings area makes it easy to use auto-tagging with multiple AdWords accounts and import your AdWords data into Google Analytics.
To see setup instructions please visit the official Google Analytics blog.
Improvements to applying AdWords account data to multiple profiles
Now that you can link multiple AdWords accounts to Google Analytics, Google have also made it easier import your AdWords data into multiple profiles in Google Analytics.
Here is a quick video demonstrating how to do this: